Encoding method and encoding apparatus, and computer program and computer readable storage medium

Abstract

This invention re-encodes encoded data (e.g., PackBits encoded data), which is expressed by a data format of a runlength code part indicating the runlength of the same data and a data part indicating the data, and a runlength code part indicating the runlength of a different data stream and a data part indicating the different data stream, to the same data format without decoding that encoded data, thereby improving a compression ratio. To this end, upon reception of data encoded by a PackBits encoding process, a data division unit separates that data into information indicating the runlength of data, and a data part, and outputs them as num and data. A data processing unit masks a predetermined bit in accordance with an instruction from a monitor unit, and outputs that result to a data combining unit. The data combining unit and a data output unit reconstruct and output data in the PackBits format in accordance with the masked data part and num data.

1. An encoding method for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, and a runlength code part indicating a runlength of different data and a data part indicating the different data, to that data format, comprising:
 a step of inputting encoded data in the data format;  
 a step of separating a runlength code part and a data part from the encoded data;  
 a step of changing a desired bit in the separated data part;  
 a step of reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data; and  
 a step of outputting the reconstructed data as re-encoded data.  
 
   
   
     2. The method according to  claim 1 , further comprising a step of designating a bit position to be changed in said step of changing a desired bit. 
   
   
     3. The method according to  claim 2 , wherein said designation step includes a step of designating a bit position to be changed on the basis of predetermined bit information of the data part. 
   
   
     4. The method according to  claim 1 , wherein the data part of the encoded data is formed of flag bits of a plurality of image area attributes of a pixel of image data. 
   
   
     5. The method according to  claim 1 , wherein the data part of the encoded data is data obtained by encoding image data. 
   
   
     6. The method according to  claim 1 , wherein the encoded data is PackBits encoded data. 
   
   
     7. An encoding apparatus for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, and a runlength code part indicating a runlength of different data and a data part indicating the different data, to that data format, comprising:
 input means for inputting encoded data in the data format;  
 separation means for separating a runlength code part and a data part from the input encoded data;  
 change means for changing a desired bit in the separated data part;  
 reconstruction means for reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data; and  
 output means for outputting the reconstructed data as re-encoded data.  
 
   
   
     8. A computer program functioning as an encoding apparatus for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, and a runlength code part indicating a runlength of different data and a data part indicating the different data, to that data format, said program functioning as:
 input means for inputting encoded data in the data format;  
 separation means for separating a runlength code part and a data part from the input encoded data;  
 change means for changing a desired bit in the separated data part;  
 reconstruction means for reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data; and  
 output means for outputting the reconstructed data as re-encoded data.  
 
   
   
     9. A computer readable storage medium storing a computer program of  claim 8 . 
   
   
     10. An image forming apparatus comprising:
 an image compression encoding unit, adapted to compression encode image data for one page and to store encoded image data in a first storage unit;  
 an image area determination unit, adapted to determine an image area of each pixel data of the image data, information indicating an image area determination result being 1 byte data, and determination results for respective image area types being assigned to respective bits;  
 an image area compression encoding unit, adapted to compression-encode the image area information of each pixel obtained by said image area determination unit, and to store the encoded image area information in a second storage unit;  
 a decoding unit, adapted to decode the encoded data stored in the first storage unit and the encoded data stored in the second storage unit; and  
 a print unit, adapted to correct the decoded image data on the basis of the decoded image area information, and print the corrected image data,  
 wherein said image area compression encoding unit comprises: 
 a mask unit, adapted to mask a desired bit of the image area information of one pixel obtained from said image area determination unit;  
 a PackBits encoder, adapted to PackBits encode the image area information masked by said mask unit, and store the PackBits encoded image area information in the second storage unit; and  
 a monitor unit, adapted to monitor a code size in the second storage unit, and, when the PackBits code size stored in the second storage unit reaches a predetermined size during encoding of image area information for one page, re-encode PackBits encoded data stored in the second storage unit by masking a predetermined bit of a data part of the PackBits encoded data, re storing the re-encoded data in the second storage unit, and setting said mask unit to mask the predetermined bit of image area information to be input subsequently.  
 
 
   
   
     11. A method of controlling an image forming apparatus comprising:
 an image compression encoding step, of compression encoding image data for one page and storing encoded image data in a first storage unit;  
 an image area determination step, of determining an image area of each pixel data of the image data, information indicating an image area determination result being 1 byte data, and determination results for respective image area types being assigned to respective bits;  
 an image area compression encoding step, of compression encoding the image area information of each pixel obtained in said image area determination step, and storing the encoded image area information in a second storage unit;  
 a decoding step, of decoding the encoded data stored in the first storage unit and the encoded data stored in the second storage unit; and  
 a print step, of correcting the decoded image data on the basis of the decoded image area information, and printing the corrected image data,  
 in which said image area compression encoding step comprises: 
 a mask step, of masking a desired bit of the image area information of one pixel obtained in the image area determination step;  
 a PackBits encoding step, of PackBits-encoding the image area information masked in the mask step, and storing the PackBits encoded image area information in the second storage unit; and  
 a monitor step, of monitoring a code size in the second storage unit, re-encoding, when the PackBits code size stored in the second storage unit reaches a predetermined size during encoding of image area information for one page, PackBits encoded data stored in the second storage unit by masking a predetermined bit of a data part of the PackBits encoded data, re-storing the re-encoded data in the second storage unit, and setting said mask step to mask the predetermined bit of image area information to be input subsequently.  
 
 
   
   
     12. An encoding method for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, to the data format, comprising:
 a step of inputting encoded data in the data format;  
 a step of acquiring a runlength code part and a data part from the input encoded data;  
 a step of changing a desired part in the acquired data part; and  
 a step of reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data.  
 
   
   
     13. The method according to  claim 12 , wherein, in said changing step, the different data parts of a plurality of encoded data are changed so as to hold the same data part. 
   
   
     14. The method according to  claim 12 , wherein, in said changing step, a desired bit in the acquired data part is changed. 
   
   
     15. The method according to  claim 12 , wherein the encoded data is data represented by encoding attributes of image data. 
   
   
     16. The method according to  claim 12 , wherein the encoded data is PackBits encoded data. 
   
   
     17. An encoding apparatus for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, to the data format, comprising:
 input means for inputting encoded data in the data format;  
 acquisition means for acquiring a runlength code part and a data part from the input encoded data;  
 changing means for changing a desired part in the acquired data part; and reconstruction means for reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data.  
 
   
   
     18. A computer program functioning as an encoding apparatus for re-encoding encoded data, which is represented by a data format of a runlength code part indicating a runlength of the same data and a data part indicating the data, to the data format, said program functioning as:
 input means for inputting encoded data in the data format;  
 acquisition means for acquiring a runlength code part and a data part from the input encoded data;  
 changing means for changing a desired part in the acquired data part; and  
 reconstruction means for reconstructing the data format on the basis of the changed data part and the runlength code part without decoding the input encoded data.